1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method for depositing a silicon nitride layer by allowing DCS and NH3 to react with each other at a low temperature capable of preventing device characteristics from being deteriorated.
2. Description of the Prior Art
When fabricating semiconductor devices, silicon oxide layers and silicon nitride layers are generally used as insulation layers. The silicon oxide layers and silicon nitride layers are used as buffer layers capable of insulating between electrodes and planarizing a pattern. The silicon nitride layer has a superior etching selectivity against the silicon oxide layer so that the silicon nitride layer is used as a barrier when a contact etching process or a chemical mechanical polishing process is carried out. In addition, the silicon nitride layer has a superior dielectric characteristic, so the silicon nitride layer is used for fabricating a capacitor.
When fabricating the semiconductor device, in a case of a DRAM, the silicon deposition process is achieved through 5 to 10 silicon deposition steps. According to a current tendency, the silicon deposition steps may be further increased.
The silicon nitride layer deposition process is carried out by using (1) SiH4 and NH3, or (2) DCS (Si2H2Cl2) and NH3, and source gas used for the deposition process is varied depending on a purpose for depositing the silicon nitride layer.
When SiH4 is used, since SiH4 has superior responsibility, the deposition process is carried out at a high speed and a particle control is easily achieved. However, the silicon nitride layer is not uniformly deposited over the whole area of a wafer, so a weak loading effect is represented.
In contrast, if DCS is used, the silicon nitride layer is evenly deposited over the whole area of the wafer so that superior loading effect is represented. Thus, DCS is widely used in a device having high pattern density. However, since it is required to supply great energy for dissolving DCS, a deposition speed becomes low and powdered particles may be created due to additives, such as NH4Cl. In addition, the deposition process may be performed only under high temperature conditions.
When performing the silicon nitride layer deposition process by using DCS, DCS and NH3, which are source gases, must be dissolved in order to allow DCS to react with NH3 However, in a general semiconductor manufacturing process, a deposition temperature is about 600 to 800° C. DCS cannot be sufficiently dissolved in the above temperature. In addition, it is difficult to increase the deposition temperature because a high temperature may deteriorate device characteristics.
That is, if the deposition temperature is increased above the DCS dissolving temperature, a metal electrode is deformed so that a device characteristic is deteriorated. In addition, a great amount of NH4CL powder may be created due to a reaction between DCS and NH3. The NH4CL powder may act as a particle source so that it is impossible to use the above deposition process.
As mentioned above, when manufacturing a semiconductor device, a metal layer is commonly used and a low-temperature thermal process is necessarily required. Thus, even though DCC represents various superior characteristics as mentioned above, there is a limitation if the silicon nitride layer deposition process is carried out by using DCS, because DCS can be deposited only at a high temperature.